Temperature sensing of flowing liquid

ABSTRACT

Apparatus for sensing the temperature of a flowing liquid includes a molded plastic fitting having a stream divider extending across a liquid flow passage. A temperature sensor encapsulated in the stream divider senses the temperature of a liquid stream flowing through the passage as the stream is split to flow past the stream divider.

BACKGROUND OF THE INVENTION

This application relates to the art of temperature sensing and, moreparticularly, to temperature sensing of a flowing liquid. The inventionis particularly applicable for use in sensing the temperature of waterflowing to a clothes washing machine and will be described with specificreference thereto. However, it will be appreciated that the inventionhas broader aspects and can be used for sensing the temperature of otherflowing liquids in other environments.

The temperature of the hot and cold water supplied to a washing machinevaries greatly. For example, in many geographical areas, the cold watersupply often has a much lower temperature during winter than duringsummer. The temperature of the hot water supply varies greatly from onehousehold to another depending on the setting of the hot water heaterand the distance that the washing machine is located from the waterheater. Also, there is often a difference in the flow rates of the hotand cold water. For these reasons, simply opening both the hot and coldwater valves one hundred percent to supply warm water results in anactual warm water temperature that has extremely wide variations. Waterthat is too hot may damage certain clothes and water that is too coldmay not clean effectively. In addition, the unnecessary use of excessivehot water is energy inefficient and environmentally unfriendly.Therefore, it would be desirable to have an arrangement for accuratelysensing the temperature of warm water being supplied to a washingmachine in order to cycle or modulate at least the hot water valve andthereby maintain a relatively constant warm water temperature.

SUMMARY OF THE INVENTION

In accordance with the present application, a stream divider is moldedacross the liquid flow passage of a molded plastic fitting. A thermistoris encapsulated in the stream divider for sensing the temperature ofliquid flowing therepast. The change in resistance of the thermistorwith temperature is sensed by an electronic control that then cycles ormodulates at least the hot water value to maintain a relatively constanttemperature of the liquid flowing through the fitting.

In a preferred arrangement, the stream divider is centrally locatedbetween opposite ends of the flow passage in the fitting. The streamdivider also extends diametrically across the cylindrical flow passageand divides the passage into two equal areas that have a combinedcross-sectional area that is between 35-65% of the cross-sectional areaof the flow passage.

The stream divider preferably has somewhat of an airfoil shape tominimize turbulent flow and effectively split the flowing stream to flowaround and past the stream divider in intimate contact therewith.

It is a principal object of the present invention to provide an improvedfitting for sensing the temperature of liquid flowing through thefitting.

It is another object of the invention to provide an improved fittinghaving a stream divider extending across an internal cylindrical flowpassage and with a thermistor encapsulated in the stream divider.

It is another object of the invention to provide a one-piece moldedplastic fitting having a thermistor molded within a flow passage in thefitting.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of a washing machine water supply andcontrol with the improved fitting of the present applicationincorporated therein;

FIG. 2 is a side elevational view of a thermistor attached to a pair ofelectrical leads;

FIG. 3 is a top plan view of a chill shot of plastic materialsurrounding the thermistor, crimp connectors and end portions of theelectrical leads to which the thermistor is attached;

FIG. 4 is a side elevational view of the chill shot of FIG. 3;

FIG. 5 is a top plan view of a molded plastic fitting constructed inaccordance with the present application;

FIG. 6 is a cross-sectional elevational view taken generally on line6--6 of FIG. 5;

FIG. 7 is a cross-sectional elevational view taken generally on line7--7 of FIG. 6;

FIG. 8 is a cross-sectional elevational view taken generally on line8--8 of FIG. 5; and

FIG. 9 is a partial cross-sectional elevational view taken generally online 9--9 of FIG. 8 and with portions omitted to show only the streamdivider.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawing, wherein showings are for purposes ofillustrating a preferred embodiment of the invention only and not forpurposes of limiting same, FIG. 1 shows a receptacle A such as a tub fora clothes washing machine. Hot and cold water supply lines 10 and 12 areconnected with motorized or solenoid operated hot and cold water supplyvalves 14 and 16. Hot and cold water from valves 14 and 16 is dischargedthrough conduits 18 and 20 to a mixing chamber 22 having an outlet 24. Afitting B in accordance with the present application is connected withoutlet 24 and discharges through outlet 26 into receptacle A.

An electronic control C is connected by electrical leads 30 and 32 withhot water valve 14, and by electrical leads 34 and 36 with cold watervalve 16. It will be recognized that it is not always necessary toconnect cold water valve 16 with electronic control C because it ispossible for many purposes to regulate the temperature of waterdischarged from mixing chamber 22 by modulating or cycling only hotwater valve 14. Electrical leads 38 and 40 connect electronic control Cwith a thermistor in fitting B.

Electronic control C may have manually operable buttons 50, 52 and 54for selecting hot, warm and cold water temperatures. Selecting hotbutton 50 leaves cold water valve 16 closed so that all of the watersupplied to receptacle A flows through hot water valve 14. Selection ofcold water button 54 leaves hot water valve 14 closed so that all of thewater supplied to receptacle A flows through cold water valve 16.Selection of warm water button 52 opens both hot and cold water valves14 and 16. Only the hot water valve or both of valves 14 and 16 then arecycled or modulated by feedback signals from the thermistor withinfitting B to maintain the temperature of the mixed hot and cold water atthe setting in the control. The resistance of the thermistor varies withtemperature and is proportional to the temperature of the water flowinginto receptacle A. Electronic control C is programmed to receive signalsfrom the thermistor and cycle or modulate the hot water supply valve orboth of the water supply valves to maintain a desired temperature forthe warm water.

FIG. 2 shows a thermistor 60 having its electrical leads attached bycrimp connectors 62 and 64 to electrical leads 66 and 68. Thermistor 60may be a glass encapsulated thermistor having a negative temperaturecoefficient. However, it will be recognized that other types ofthermistors can be used and that for some purposes thermistors having apositive temperature coefficient can be used. The thermistor provides arepeatable resistance output with temperature and the resistance isinterpreted as temperature by the software in electronic control C.

Thermistor 60, crimp connectors,62 and 64, and the end portions of leads66 and 68 adjacent to crimp connectors 62 and 64 are positioned within amold cavity. Plastic material then is injected into the mold toencapsulate the thermistor, crimp connectors and end portions of theleads within what is commonly known as a chill shot D in FIGS. 3 and 4.Chill shot D provides enlarged end portions 70 and 72 having integrallocator pins 73-76 for locating the chill shot in another mold cavityused to mold fitting B. Central portion 78 of chill shot D has a reduceddiameter relative to end portions 70 and 72, and is generallycylindrical.

When chill shot D is integrally molded into fitting B, additionalplastic material is molded around central portion 78 to make it largerand with somewhat of an airfoil configuration as generally indicated at78a in FIGS. 6 and 9.

Fitting B, as shown in FIGS. 5 and 6, has a cylindrical liquid flowpassage 80 therethrough and opposite ends 82 and 84. The generallyairfoil-shaped member 78a in which the thermistor is encapsulated nowbecomes a stream divider that splits a liquid stream flowing throughpassage 80. Stream divider 78a is centrally located between oppositeends 82 and 84, and also lies on the diameter of passage 80.

As best shown in FIG. 9, stream divider 78a has knife edges 90 and 92that face toward ends 82 and 84 of fitting B. Thus, fitting B isbidirectional and can be installed with either end facing toward themixing chamber. Knife edges 90 and 92 are located in a plane thatbisects cylindrical passage 80 longitudinally. Stream divider 78a curvesfrom knife edges 90 and 92 toward the outwardly curved midpoints 94 and96 of the divider that are on the diameter of a cylinder havingapproximately the same diameter as generally cylindrical end portions 70and 72. As shown in FIGS. 7 and 8, stream divider 78a divides passage 80into a pair of passages 102 and 104 that together have a combinedcross-sectional area that is between 35-65% of the cross-sectional areaof passage 80, and more preferably between 40-60% of the cross-sectionalarea of passage 80.

A liquid stream flowing through passage 80 and fitting B is split by aknife edge 90 or 92 into two streams that flow through smaller areas 102and 104 to rejoin into one stream on the opposite side of the streamdivider. Thermistor 60 is in intimate contact with the flowing liquidfor accurate temperature sensing to modulate or cycle at least the hotwater valve and maintain a more accurate temperature for the warm watersupplied to receptacle A. The airfoil shape of the stream dividerminimizes turbulent flow so that the water remains in contact with theouter surfaces of the stream divider for better heat transfer to thethermistor.

Although the invention has been shown and described with respect to apreferred embodiment, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of this specification. The present invention includesall such equivalent alterations and modifications, and is limited onlyby the scope of the claims.

I claim:
 1. An apparatus for sensing the temperature of a flowing liquidcomprising a fitting molded from a plastic material and having a liquidflow passage therethrough, a temperature sensor molded into said fittingin a position extending across said passage internally of said fitting,said temperature sensor being positioned for splitting a single liquidstream flowing through said passage into two liquid streams as theliquid stream flows past said temperature sensor.
 2. The apparatus ofclaim 1 wherein said temperature sensor is positioned for splitting asingle liquid stream flowing through said passage into two liquidstreams having substantially the same cross-sectional area.
 3. Theapparatus of claim 1 wherein said temperature sensor has oppositeelectrical leads projecting externally of said fitting.
 4. The apparatusof claim 1 wherein said passage is cylindrical and has a longitudinalaxis, and said temperature sensor being positioned in intersection withsaid longitudinal axis.
 5. The apparatus of claim 1 wherein said passagehas opposite ends and said temperature sensor is positionedsubstantially midway between said opposite ends.
 6. The apparatus ofclaim 1 wherein said passage has a passage cross-sectional area and saidtemperature sensor divides said passages into a pair of passages havinga combined cross-sectional area that is between 35-65% of said passagecross-sectional area.
 7. The apparatus of claim 1 wherein saidtemperature sensor comprises a thermistor.
 8. The apparatus of claim 1wherein said temperature sensor is encapsulated in plastic that has across-sectional profile for minimizing turbulent flow therepast.
 9. Theapparatus of claim 8 wherein said cross-sectional profile includes aleading edge that faces upstream of liquid flow and has a substantiallyknife edged shape.
 10. A molded temperature sensing hose fittingcomprising a substantially cylindrical plastic body having a cylindricalliquid flow passage therethrough, said passage having a longitudinalaxis and a passage diameter, a plastic stream divider molded into saidfitting and extending across said passage of said fitting to divide saidcylindrical passage into a pair of passages that extend past saiddivider, and a temperature sensor encapsulated in said stream divider.11. The fitting of claim 10 wherein said plastic stream divider extendssubstantially diametrically of said passage.
 12. The fitting of claim 10wherein said pair of passages together have an area that is between40-60% of the area of said passage.
 13. The fitting of claim 10 whereinsaid temperature sensor has opposite electrical terminals thereonprojecting externally of said fitting.
 14. The fitting of claim 10wherein said cross-sectional profile includes a leading edge that facesupstream of liquid flow and has a substantially knife edged shape. 15.In a clothes washing machine having a tub to which water is suppliedthrough electrically operated hot and cold water valves, said machineincluding an electronic control having a warm water setting in whichboth of the hot and cold water valves are opened to supply warm water tothe tub, said machine including a molded plastic fitting between saidtub and said valves, said fitting having a flow passage through whichwater flows from said valves to said tub, a molded plastic streamdivider molded into said fitting and extending across said passage todivide a single stream flowing through said passage into two streamsthat flow past said stream divider, said stream divider having a crosssectional profile that minimizes turbulent flow therepast, a thermistorencapsulated in said stream divider and connected with said control toprovide feedback signals related to water temperature, said controlbeing responsive to said feedback signals to modulate at least said hotwater valve and regulate the temperature of mixed hot and cold waterflowing through said passage in said fitting.